In a new film for the #oktosay series of their joint Heads Together mental health campaign, the trio of royals sat outside at Kensington Palace for an intimate conversation about the topics that have hit them the hardest. For the men, that meant the death of their mother, Princess Diana.

"Harry and I over the years have not talked enough about our mother," Prince William admitted to his wife. The Princess of Wales tragically died in 1997, nearly 20 years ago this August.

As Prince Harry has opened up about already recently, he said he shut out memories of his late mom for two decades. But, as the brothers addressed in their candid chat, they rarely even spoke about the significant and startling loss.

"We've never really talked about losing a mom at such a young age," Harry said. "When you speak to other people's families and little kids and stuff, you think, 'Wow, I don't want them to have to go through the same things'...with a little bit of experience, you want to help as much as you can and try and empower them to have that conversation and to be brave enough for themselves to talk about it at a young age rather than bottling it up for far too long."

It was because of his older brother that he stopped bottling it up himself. "I always thought to myself, "What's the point of bringing up the past? What's the point of bringing up something that's only going to make you sad. It ain't going to change it. It ain't going to bring her back.' And when you start thinking like that, it can be really damaging," he recalled. "[William] always said to me, [he] said, 'You've got to sit down and think about those memories.' But, for me, it was like I don't want to think about it.'"

As they continue their service work and encourage everyone to partake in those difficult conversations, they're practicing what they preach as a family.

"We have been brought closer because of the circumstances," William pointed out. "[We] are uniquely bonded because of what we've been through."